1. Field of the Invention
The present invention relates to apparatus for measuring the calorific power of hydrocarbon compounds such as crude oil and petroleum products.
2. Description of the Prior Art
Calorific power is an important measure to determine the quality of crude oil and petroleum products. For example, in a power plant where a large amount of petroleum fuel is consumed, the calorific power of the fuel used is a significant factor in determining the cost of the power generated. This circumstance has called for the most precise calorific power measurement or analysis, which, however, has been dependent upon manual processes even in a highly automated power plant. One well-known calorific power measuring method uses an adiabatic bomb wherein a given amount of petroleum is burned to measure the calorific power. In this method the calorific power can be measured directly, but at the sacrifice of time taken for measuring preparations and procedures. Furthermore, this method requires the use of a precision thermometer to detect very small temperature variations, and measuring accuracy is significantly affected by the manner of measurement and the instruments used.
Another method of measuring the calorific power of a hydrocarbon compound uses neutrons and proceeds on the principle that the hydrogen atomic nucleus in crude oil has the prime decelerating effect on the neutron. The density of the hydrocarbon atomic nuclei is measured through measurement of thermal neutrons generated by the deceleration and the calorific power is approximately measured by the use of a nearly constant carbon-to-hydrogen weight ratio. This method permits continuous calorific power measurement without the necessity of extracting a sample of the process hydrocarbon compound, with the result that labor is saved and the measuring accuracy is independent of a technician's personal skill. However, because this method is primarily intended to measure the density of hydrogen atomic nuclei, some measuring error is inevitable if a third substance such as sulfur is present in the process hydrocarbon compound, which leads to changes in the carbon-to-hydrogen concentration ratio. Furthermore, the neutron detecting instrument used in this method is generally of low stability and often causes measuring error. In addition, when exposed to neutrons, a substance is caused to radiate gamma rays which are dangerous to man and can give rise to measuring error.